Method and composition for the bright coating of zinc



Patented Jan. 10, 1939 PATENT OFFICE METHOD AND COMPOSITION FOR THE BRIGHT COATING OF ZINC Leroy Camel; Maple Heights, Ohio, assignor to The Plating and Galvanizing Company, Cleveland, Ohio, a corporation of Ohio No Drawing.

Application December 11, 1936,

Serial No. 115,350 4 4 Claims.

This invention, as indicated, relates to a method and composition for the bright coating of zinc, preferably upon articles of a ferrous character, More particularly, it comprises a composition adapted to bring about the bright plating of zincor zinc associated with other metals, and the method of carrying on such operation with a single plating bath producing a bright finished article on a quantity production basis with a uniform quality of product.

Heretofore coating of articles with zinc from cyanide solutions has been carried out, but in most instances such coatings, where satisfactory adherence to the surface has been brought about, have been of a dull color, or when such coatings have been relatively bright, they involved a bright dipping operation as a finishing step.

The present invention provides a composition for a zinc plating bath from which zinc is adapted to be applied as a coating to various articles to serve as a protective surface therefor as well as presenting a surface of relatively high luster and smoothness,

In its broader aspect, the invention comprises the electro-deposition of zinc from a sodium zinc cyanide bath, with active sodium alkali in the form of sodium hydroxide present, and sodium salts, preferably sodium sulphite, serving as addition agents. The addition of nickel in the form of a salt adds conductivity to the bath, and may form a slight alloy with the zinc. The nickel may be incorporated in the zinc anode or may be supplied to the bath in metallic form. However, it is preferably added as a nickel salt, such as nickel sulphate, the amount being held within a range of .2 to 1 ounce per gallon of water.

The preferred form of the invention comprises the addition of sodium cyanide and zinc cyanide to a bath of water in the amounts of preferably 5 to 8 ounces per gallon of water for each of such substances, and the addition of sodium hydroxide between the amounts of 9 to 12 ounces per gallon of water. Metallic zinc may be used in place of zinc cyanide. As a brightener sodium sulphite alone may be used, the amount varying from .5 to 2 ounces per gallon of Water. However, it is preferred to use in conjunction with the sodium sulphite, a sodium hyposulphite in the amount of 1.5 ounces per gallon of water, where the amount of sodium sulphite used is .5 ounce per gallon of water. The combination of sodium sulphite and sodium hyposulphite apparently produces a greater brightness and uniformity of result than the sodium sulphite used alone. An

a saving of time as well as labor cost is brought about through the use of the nickel element in small amounts, and articles plated have a brightness equal to articles which are specially treated with a finishing dip for the purpose of brightening.

While the proportions for making up the electrolyte are not critical, as has been indicated, it is believed that through the use of the following exact proportions of ingredients the most satisfactory results can be obtained, inasmuch as such formula has been the basis of extended tests.

Sodium cyanide ounces per gallon of water 7.37 Zinc cyanide do 6.57 Inactive carbonates do .63 Sodium hydroxide do 12 Sodium sulphite do .5 Sodium hyposulphite do 1.5 Nickel sulphate do .2128 Water gallon 1 The materials are preferably added to the water in the order named, each substance being fully dissolved prior to the addition of the succeeding compound. However, a mixture of dry ingredients may be added to the bath slowly, such ingradients including all of the elements specified in finely divided form.

The sodium hyposulphite and nickel sulphate in conjunction with the sodium sulphite serve to bring about the high luster coating action of the electrolyte. A pure metallic zinc anode preferably is utilized, and from time to time replace-- ment will be required of the same, as well as certain ingredients of the bath, particularly sodium cyanide.

The bath, when fully prepared, will be found to permit the use of a current of up to 45 amperes in the plating circuit or as low as amperes per square foot of surface at preferably from 4 to 6-volts. The anode utilized preferably comprises pure zinc. At a temperature of between 60 and 90 Fahrenheit, the plating bath above set forth will coat ferrous articles with a satisfactory coating in approximately ten minutes, and such coating will be closely adherent to the surface treated, of fine grain, and of smooth bright texture.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the means and steps herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In the art of zinc plating, the process which comprises electroplating zinc. from a sodium zinc cyanide bath containing active sodium hydroxide in the presence of addition agents comprising sodium sulphite in the amount of 0.5 ounce per gallon of water and sodium hyposulphite in the amount of 1.5 ounces per gallon of Water.

2. In the art of zinc plating, the process which comprises electroplating zinc from a sodium zinc cyanide bath containing active sodium hydroxide ing containing active sodium hydroxide sodium sulphite to the amount of approximately .5 ounce per gallon of water, and sodium hyposulphite to the amount of 1.5 ounces per gallon of water and nickel sulphate to the amount of .2128 ounce per gallon of water.

LEROY CAMEL. 

